Composite Fresnel acoustic lens, design method and related equipment

Abstract

The invention relates to the technical field of Fresnel acoustic lens application, and provides a composite Fresnel acoustic lens, a design method and related equipment. The composite Fresnel acoustic lens comprises at least two groups of coaxial multi-focus Fresnel zone plates, the at least two groups of coaxial multi-focus Fresnel zone plates are translated for a set distance along the radial direction and then are superposed, at least three non-coaxial ultrasonic focuses are generated in a three-dimensional space, and the composite Fresnel acoustic lens can be used for transcranial ultrasonic stimulation or treatment; wherein the coaxial multi-focus Fresnel area plate comprises a plurality of layers of lens structures which are nested together, and the plurality of layers of lens structures comprise a frame area and an ultrasonic transmission medium area. According to the invention, through a method of superposing a plurality of groups of coaxial multi-focus Fresnel zone plates, simultaneous focusing of a plurality of ultrasonic target spots with different axes and different depths is realized, and the limitation of limited coverage range of a traditional single focus or coaxial bifocus is overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of the application of Fresnel acoustic lenses, and particularly to a composite Fresnel acoustic lens, a design method and related equipment. Background Art

[0002] The statements in this part merely provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] Transcranial Focused Ultrasound (TcFUS) is a technology that uses ultrasonic waves to focus in the skull for treatment and is widely used in the research of diseases such as Alzheimer's disease, epilepsy, and Parkinson's syndrome. Due to the special structure of the skull, ultrasonic waves are prone to acoustic attenuation and phase distortion during penetration, resulting in limited treatment effects. In the prior art, a variety of methods have been proposed to compensate for the phase error and energy loss of ultrasonic waves, such as phased array method, time reversal method, and acoustic lens, etc. However, these methods are usually computationally complex or have problems such as insufficient mechanical stability and low focusing efficiency.

[0004] In addition, most brain disease treatments and brain regulations often require the coordinated action of multiple brain regions, that is, ultrasonic stimulation needs to be given to multiple brain regions simultaneously. In the design of planar acoustic lenses, the existing Fresnel acoustic lens structure usually can only generate one focal point and it is difficult to achieve flexible coverage of multiple targets in space. Summary of the Invention

[0005] In order to solve the technical problems in the above background art, the present invention provides a composite Fresnel acoustic lens, a design method and related equipment. The present invention realizes the simultaneous focusing on multiple ultrasonic targets with different axes and different depths by superimposing multiple groups of coaxial multi-focus Fresnel zone plates, overcomes the limitation of the limited coverage range of traditional single-focus lenses, and at the same time allows customized design according to the ultrasonic frequency and the position of the brain regions involved in the treatment, improving the applicability, personalization and effect of transcranial ultrasound treatment.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a composite Fresnel acoustic lens.

[0008] A composite Fresnel acoustic lens, comprising: at least two groups of coaxial multi-focus Fresnel zone plates, which are superimposed after being translated radially along the coaxial multi-focus Fresnel zone plates to generate at least three non-coaxial ultrasonic focal points in three-dimensional space, and can be used for transcranial ultrasound stimulation or treatment of the brain;

[0009] Wherein, the coaxial multi-focus Fresnel zone plate includes a multi-layer lens structure nested together, and the multi-layer lens structure includes a border area and an ultrasonic transmission medium area.

[0010] Further, by superimposing at least two groups of coaxial multi-focus Fresnel zone plates in a superimposed manner to generate a superimposed composite Fresnel acoustic lens, the overlapping area is retained during the superposition.

[0011] Further, the superimposed composite Fresnel acoustic lens includes a first frame area and a first ultrasonic transmission medium area, and the first frame area is formed by radially translating and superimposing at least two groups of identical coaxial multi-focus Fresnel zone plates.

[0012] Further, by removing the overlapping area after superimposing at least two groups of coaxial multi-focus Fresnel zone plates and setting rectangular support structures at certain positions, an alternately segmented composite Fresnel acoustic lens is generated.

[0013] Further, the alternately segmented composite Fresnel acoustic lens includes a second frame area, a second ultrasonic transmission medium area and a rectangular support structure.

[0014] The second aspect of the present invention provides a design method for a composite Fresnel acoustic lens.

[0015] A design method for the composite Fresnel acoustic lens described in the first aspect, comprising:

[0016] Selecting coaxial foci from preset foci to obtain multiple coaxial multi-focus groups for constructing a coaxial multi-focus Fresnel zone plate; the process of constructing the coaxial multi-focus Fresnel zone plate includes:

[0017] For each coaxial multi-focus group, arranging the foci in ascending order of focal length: each focus corresponds to a lens structure layer, the lens structure with a smaller focal length is located in the inner layer, and the lens structure with a larger focal length is located in the outer layer;

[0018] Based on the ultrasonic wavelength and the preset focal lengths of the foci, using the Fresnel half-wave zone theory, calculating the radii of the respective Fresnel zones corresponding to each focus, the radii of the Fresnel zones including: the radii corresponding to odd zone numbers and the radii corresponding to even zone numbers; setting the radii corresponding to odd zone numbers as the inner diameters of the frame areas of the corresponding lens structures and the radii corresponding to even zone numbers as the outer diameters of the frame areas of the corresponding lens structures;

[0019] Nesting the lens structures corresponding to each focus, and selecting the number of Fresnel zones of each layer of lens structure under the principle that the outer diameter of the frame area corresponding to the maximum number of zones of the inner layer lens structure is less than the inner diameter of the frame area corresponding to the minimum number of zones of the outer layer lens structure, to construct a coaxial multi-focus Fresnel zone plate capable of generating coaxial multi-foci.

[0020] At least two sets of coaxial multi-focus Fresnel zone plates capable of generating coaxial multi-foci are translated radially by a set distance and then superimposed to construct a composite Fresnel acoustic lens; the processing methods after superimposition include: retaining the overlapping area during superimposition to generate a superimposed composite Fresnel acoustic lens; after superimposition, in a way of removing the overlapping area and setting rectangular support structures at certain positions to generate an alternately segmented composite Fresnel acoustic lens.

[0021] The third aspect of the present invention provides a cranial window replacement system.

[0022] A cranial window replacement system uses the composite Fresnel acoustic lens described in the first aspect to replace a part of the skull, and plane ultrasound forms at least three focal spots in the cranial cavity through the composite Fresnel acoustic lens.

[0023] Furthermore, the composite Fresnel acoustic lens is fixed to the edge of the cranial window through a biocompatible adhesive to replace the missing skull. One side of the composite Fresnel acoustic lens is close to the brain area, and the other side is connected to a plane ultrasound transducer.

[0024] Furthermore, the materials of the first border area, the second border area, the first ultrasonic transmission medium area, the second ultrasonic transmission medium area, and the rectangular support structure in the composite Fresnel acoustic lens are all biocompatible materials.

[0025] The fourth aspect of the present invention provides a plane ultrasound transducer accessory.

[0026] A plane ultrasound transducer accessory includes: the composite Fresnel acoustic lens described in the first aspect. A secondary support fixture module and a main support fixture base are symmetrically arranged on both sides of the composite Fresnel acoustic lens. A rectangular clamping cavity is provided inside the main support fixture base, and its inner contour matches the outer dimension of the secondary support fixture module. Rigid locking is achieved by axially embedding the secondary support fixture module into the rectangular clamping cavity. The main support fixture base and the transducer-base connection column adopt an integrated connection structure. The transducer-base connection column sleeves the outer periphery of the plane ultrasound transducer and has an interference fit with the plane ultrasound transducer. The composite Fresnel acoustic lens is nested on the transducer-base connection column.

[0027] Furthermore, the inner diameter tolerance of the transducer-base connection column and the outer diameter tolerance of the plane ultrasound transducer meet the requirements of interference fit.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] In view of the technical problem that the existing Fresnel acoustic lens structure can usually generate only one focus or two coaxial foci, the present invention provides a composite Fresnel acoustic lens. By superimposing multiple groups of coaxial multi-focus Fresnel zone plates, simultaneous focusing on multiple ultrasonic target points with different axes and different depths in three-dimensional space is achieved, overcoming the limitation of the limited coverage range of traditional single-focus lenses. The present invention provides two design schemes, namely, a superimposed type and an alternating segmentation type, which can be selected according to specific application requirements, enhancing the flexibility and applicability of the design. The cranial window structure of the composite Fresnel acoustic lens of the present invention can replace part of the skull. Under the same energy density, it can achieve better ultrasonic brain function stimulation and treatment, providing a feasible path for a more comprehensive and efficient treatment plan for multiple brain lesion regions, and having broad application prospects. The planar ultrasonic transducer accessory of the present invention can be customized according to the requirements of the application scenario to achieve personalized ultrasonic focusing and application.

[0030] In view of the technical problem that due to the special structure of the skull, ultrasonic waves are prone to acoustic attenuation and phase distortion during penetration, resulting in limited treatment effects, the present invention uses a composite Fresnel acoustic lens cranial window to replace part of the skull, replacing the skull with irregular material and large acoustic impedance with a regular cranial window with small acoustic impedance, reducing the distortion and attenuation degree of ultrasonic signals by the skull.

[0031] In view of the technical problems of large computational complexity and high cost of conventional phased array methods and time reversal methods, the present invention uses a composite Fresnel acoustic lens to replace the skull or as a planar ultrasonic transducer accessory to achieve comprehensive, efficient and personalized ultrasonic brain function regulation and treatment, and uses the regular geometric shape of the composite Fresnel acoustic lens cranial window structure to reduce the computational complexity and hardware cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0033] Figure 1 Schematic structural diagram of a coaxial double-focus Fresnel zone plate shown for the present invention;

[0034] Figure 2 Schematic structural diagram of a superimposed type composite Fresnel acoustic lens shown for the present invention;

[0035] Figure 3 Schematic structural diagram of an alternating segmentation type composite Fresnel acoustic lens shown for the present invention;

[0036] Figure 4 Simulation sound field diagram of a superimposed type composite Fresnel acoustic lens shown for the present invention;

[0037] Figure 5The simulated sound field diagram of the alternating segmentation type composite Fresnel acoustic lens shown for the present invention;

[0038] Figure 6 The schematic diagram of the composite Fresnel acoustic lens shown for the present invention as a cranial window replacing the skull;

[0039] Figure 7 The schematic diagram of the composite Fresnel acoustic lens shown for the present invention as an accessory of a planar ultrasonic transducer;

[0040] Explanation of reference numerals: 1. Inner lens structure; 2. Outer lens structure; 3. Demarcation line between the inner lens and the outer lens; 4. Frame area; 5. Ultrasonic transmission medium area; 6. First frame area; 7. First ultrasonic transmission medium area; 8. Second frame area; 9. Second ultrasonic transmission medium area; 10. Rectangular support structure; 11. Planar ultrasonic transducer; 12. Ultrasonic coupling agent; 13. Composite Fresnel acoustic lens; 14. Focus spot generated by the planar ultrasonic transducer after passing through the multi-focus Fresnel acoustic lens; 15. Cerebral cortex area; 16. Deep brain nuclear area; 17. Superposition type composite Fresnel acoustic lens; 18. Alternating segmentation type composite Fresnel acoustic lens; 19. Sub-support fixture module; 20. Main support fixture base; 21. Transducer-base connection column. Detailed implementation manners

[0041] The present invention will be further described below in conjunction with the drawings and embodiments.

[0042] It should be noted that the following detailed descriptions are all illustrative and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0043] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary implementation manners according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "comprise" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0044] In this embodiment, "first", "second", etc. may refer to different or the same objects. Unless clearly specified in the context, the definition of a term is consistent throughout the specification.

[0045] Embodiment 1

[0046] This embodiment provides a composite Fresnel acoustic lens, comprising: at least two groups of coaxial multi-focus Fresnel zone plates, which are superposed after being translated radially along the coaxial multi-focus Fresnel zone plates to generate at least three non-coaxial ultrasonic foci in a three-dimensional space, and can be used for transcranial ultrasonic stimulation or treatment of the brain; wherein, the coaxial multi-focus Fresnel zone plate comprises a multi-layer lens structure nested together, and the multi-layer lens structure comprises a border area and an ultrasonic transmission medium area.

[0047] Among them, at least three non-coaxial ultrasonic foci refer to: all foci may not be coaxial; or some foci may be coaxial and some foci may not be coaxial.

[0048] In some embodiments, there are two design methods for the composite Fresnel acoustic lens to achieve multiple ultrasonic foci in a three-dimensional space: (1) A superposition-type composite Fresnel acoustic lens can be generated by superposing the above two groups of coaxial multi-focus Fresnel zone plates in a superposition manner, and the overlapping area is retained during superposition; (2) By removing the overlapping area after superposing the above two groups of coaxial multi-focus Fresnel zone plates and setting a rectangular support structure, the overlapping area is removed and an alternating segmentation-type composite Fresnel acoustic lens is generated. The setting of the rectangular support follows the following standard: to ensure the overall stability and load-bearing capacity of the structure, the length of each group of rectangular supports is not shorter than the radius of the corresponding coaxial multi-focus Fresnel zone plate.

[0049] In a possible implementation manner, taking the coaxial dual-focus Fresnel zone plate as an example below, a composite Fresnel acoustic lens is designed, as Figure 1 shown. Structurally, the coaxial dual-focus Fresnel zone plate comprises: an inner lens structure 1, an outer lens structure 2, and a boundary line 3 between the inner lens and the outer lens (in actual application, the boundary line does not actually exist, and it is only for distinguishing the inner lens structure and the outer lens structure here), and both the inner lens structure 1 and the outer lens structure 2 are existing lens structures; in terms of material composition, the coaxial dual-focus Fresnel zone plate comprises: a border area 4 and an ultrasonic transmission medium area 5.

[0050] It should be noted that the number of layers of the multi-layer lens structure described in this embodiment is determined by the number of foci belonging to the same axis. When two foci are coaxial as shown in this embodiment, a double-layer lens structure is constructed. The multi-layer lens structure described in this embodiment also includes a three-layer lens structure, a four-layer lens structure, etc., which all fall within the protection scope of the present invention. Figure 1 In some embodiments, the spatial characteristics of the multiple foci generated by the composite Fresnel acoustic lens are: at least three ultrasonic foci that can simultaneously achieve coaxial and non-coaxial in a three-dimensional space.

[0051]

[0052] ​In some embodiments, the multi-foci generated by the composite Fresnel acoustic lens have simultaneity, stability, and robustness.

[0053] In some embodiments, the number of multi-foci generated by the composite Fresnel acoustic lens is ≥ 3.

[0054] In some embodiments, the application scenarios of the composite Fresnel acoustic lens include, but are not limited to, brain ultrasound stimulation or treatment, and other scenarios that require multi-focus ultrasound focusing are also included.

[0055] In some embodiments, the usage methods of the composite Fresnel acoustic lens include, but are not limited to: replacing part of the skull structure as an implantable cranial window, and being used as a replaceable accessory for a planar ultrasound transducer in ultrasound focusing occasions with different focusing requirements.

[0056] In some embodiments, the preparation materials of the composite Fresnel acoustic lens include, but are not limited to, the Ti-PDMS combination, where the Ti material is the border area (ultrasound reflection material), and the PDMS material is the ultrasound transmission medium area (ultrasound transmission material); combinations of other ultrasound reflection materials and ultrasound transmission materials are also possible. It should be noted that the constituent materials of the composite Fresnel acoustic lens used to replace the cranial window must meet biocompatibility requirements.

[0057] Refer to Figure 1 , the coaxial dual-focus Fresnel zone plate is composed of an inner lens structure 1 and an outer lens structure 2. The radii of the inner lens structure 1 and the outer lens structure 2 satisfy the formula:

[0058]

[0059] In the formula, r n is the radius of the nth annular Fresnel zone plate, λ is the ultrasonic wavelength, and F is the corresponding lens focal length. The inner lens structure 1 and the outer lens structure 2 are calculated by substituting different lens focal lengths into the above formula to generate two foci with different focal lengths on the axis of the coaxial dual-focus Fresnel zone plate.

[0060] Refer to Figure 2 , the stacked Fresnel acoustic lens is composed of a first border area 6 and a first ultrasound transmission medium area 7. The structure of the first border area 6 is formed by radially translating and stacking two sets of coaxial dual-focus Fresnel zone plates with the same structure. Its transmitted sound field intensity satisfies the Rayleigh-Sommerfeld diffraction integral formula:

[0061]

[0062] In the formula, I(x, y, z) is the sound intensity at the three-dimensional space coordinate target (x, y, z), and λ is the ultrasonic wavelength. p i(',y') is the amplitude of the incident field distribution in front of the superposition type composite Fresnel acoustic lens, and τ i (x′, y′) is the transmission function, which satisfies In the formula, Z1 is the acoustic impedance of the background medium, and Z2 is the acoustic impedance of the material of the first frame area 6.

[0063] Referring to Figure 3 , the alternating segmentation type composite Fresnel acoustic lens is composed of a second frame area 8, a second ultrasonic transmission medium area 9 and a rectangular support structure 10. The intensity of its transmitted sound field also satisfies the Rayleigh-Sommerfeld diffraction integral formula.

[0064] In some embodiments, the thickness of the rectangular support is the same as the thickness of the frame area to ensure sufficient bending strength; the width is preferably as small as possible while maintaining stability, and in this embodiment, the width can be 4 mm. In this embodiment, the number of the rectangular supports is 4, and they are evenly distributed at intervals of 90° along the circumferential direction. The materials of all the rectangular supports are the same as those of the frame area, and they form an integral connection with the frame area.

[0065] Referring to Figure 4 , the focused focal spot of the superposition type composite Fresnel acoustic lens is ellipsoidal, and four focal points are formed at different positions. Referring to Figure 5 , the focused focal spot of the alternating segmentation type composite Fresnel acoustic lens is also ellipsoidal, and four focal points are formed at different positions.

[0066] In this embodiment, a coaxial double-focus Fresnel zone plate is taken as an example to construct a composite Fresnel acoustic lens. In applications, a coaxial triple-focus Fresnel zone plate or a coaxial quadruple-focus Fresnel zone plate, etc. can also be used to construct a composite Fresnel acoustic lens. The specific principle is as shown above and will not be elaborated here.

[0067] The present invention realizes the simultaneous focusing on multiple ultrasonic target points with different axes and different depths by superimposing multiple groups of coaxial multi-focus Fresnel zone plates, overcoming the limitation of the limited coverage range of traditional single-focus lenses.

[0068] The present invention provides two design schemes of a superposition type composite Fresnel acoustic lens and an alternating segmentation type composite Fresnel acoustic lens, which can be selected according to specific application requirements, enhancing the flexibility and applicability of the design.

[0069] Embodiment 2

[0070] This embodiment provides a design method for a composite Fresnel acoustic lens, including:

[0071] Selecting coaxial focal points from preset focal points to obtain multiple coaxial multi-focus groups for constructing a coaxial multi-focus Fresnel zone plate; the process of constructing the coaxial multi-focus Fresnel zone plate includes:

[0072] For each coaxial multi - focus group, arrange the foci in ascending order of focal length: each focus corresponds to a layer of lens structure, the lens structure with a smaller focal length is located in the inner layer, and the lens structure with a larger focal length is located in the outer layer;

[0073] Based on the ultrasonic wavelength and the preset focal lengths of each focus, using the Fresnel half - wave zone theory, calculate the radii of each Fresnel zone corresponding to each focus. The radii of the Fresnel zones include: the radii corresponding to odd zone numbers and the radii corresponding to even zone numbers; set the radius corresponding to the odd zone number as the inner diameter of the border area of the corresponding lens structure, and set the radius corresponding to the even zone number as the outer diameter of the border area of the corresponding lens structure;

[0074] Nest the lens structures corresponding to each focus. Under the principle that the outer diameter of the border area corresponding to the maximum number of zones of the inner - layer lens structure is less than the inner diameter of the border area corresponding to the minimum number of zones of the outer - layer lens structure, select the number of Fresnel zones of each layer of lens structure to construct a coaxial multi - focus Fresnel zone plate that can generate coaxial multi - foci;

[0075] Superimpose at least two groups of coaxial multi - focus Fresnel zone plates that can generate coaxial multi - foci after translating them a set distance along the radial direction to construct a composite Fresnel acoustic lens; the processing methods after superimposition include: retaining the overlapping area during superimposition to generate a superimposed - type composite Fresnel acoustic lens; removing the overlapping area after superimposition and setting rectangular support structures at certain positions to generate an alternately segmented - type composite Fresnel acoustic lens.

[0076] The following takes an example to describe in detail the design method described in this embodiment:

[0077] Step S1: The ultrasonic wavelength λ = 1.5 mm, and the preset focal lengths of the foci with different focal lengths are F1 = 10 mm and F2 = 30 mm respectively; based on the Fresnel half - wave zone theory, use the following formula to calculate the radii of each Fresnel zone corresponding to each focus:

[0078]

[0079] where n is the zone order, and the number of Fresnel zones corresponding to each focus is obtained through this step;

[0080] Step S2: Divide the preset focus group into two categories: coaxial multi - focus groups and non - coaxial multi - focus groups. First, construct a coaxial dual - focus Fresnel zone plate that can generate coaxial dual - foci: First, for the coaxial multi - focus group, arrange the foci in ascending order of focal length, determine the focus corresponding to the inner - layer lens structure with a focal length F1 = 10 mm, and the focus corresponding to the outer - layer lens structure with F2 = 30 mm; the range of the number of Fresnel zones n of the inner - layer lens structure is 1 - 11, and the number of Fresnel zones n of the outer - layer lens structure takes 5 - 18. The inner diameter of each Fresnel zone plate is the radius r corresponding to the odd Fresnel zone number (odd zone number)2n-1 The outer diameter of each Fresnel zone plate is the radius r corresponding to the even Fresnel zone number (even zone number). 2n , where n is a positive integer. Secondly, the inner lens structure and the outer lens structure are nested, and at the same time, the outer diameter of the frame area corresponding to the maximum waveband number of the inner lens structure (15.5mm) is ensured to be smaller than the inner diameter of the frame area corresponding to the minimum waveband number of the outer lens structure (15.7mm), forming a coaxial dual-focus Fresnel zone plate (refer to Figure 1 );

[0081] Step S3: constructing a composite Fresnel acoustic lens capable of generating multiple focal points: the coaxial dual-focal point Fresnel zone plates generating coaxial multiple focal points are radially translated by a set distance and then superimposed. The processing methods after superposition include:

[0082] Method 1: Keep the overlapping area when superimposing to generate a superimposed composite Fresnel acoustic lens (refer to Figure 2 );

[0083] Method 2: Remove the overlapping area when superimposing, and set rectangular support structures at certain positions to generate an alternating split composite Fresnel acoustic lens (refer to Figure 3 ).

[0084] In this embodiment, the set distance is related to the distance between the foci of different axes, which can be 10 mm here. It should be noted that this embodiment only provides an implementation method and should not be understood as a specific limitation on the set distance. In other embodiments, the set distance can also take other values.

[0085] Embodiment 3

[0086] like Figure 6 As shown, this embodiment provides a composite Fresnel acoustic lens cranial window replacement system, which adopts the composite Fresnel acoustic lens 13 described in Example 1 to replace part of the skull, and the planar ultrasound passes through the composite Fresnel acoustic lens 13 to form at least three focal spots at the target position in the skull (the cerebral cortex area 15 and the deep brain nuclear area 16 each have two focal spots), and can simultaneously perform ultrasonic combined stimulation on the cerebral cortex 15 and the deep brain nuclear area 16 on the left and right sides. Its application scenarios include but are not limited to brain function regulation for sleep aids and ultrasonic treatment of brain diseases such as epilepsy and Alzheimer's disease.

[0087] In this embodiment, planar ultrasound can be emitted by introducing a planar ultrasound transducer 11 .

[0088] It should be noted that the constituent materials of the composite Fresnel acoustic lens 13 used to replace the cranial window must meet biocompatibility.

[0089] In some embodiments, the composite Fresnel acoustic lens 13 is fixed to the edge of the missing cranial window by a biocompatible adhesive. Its outer surface (facing the planar ultrasonic transducer) is coated with an ultrasonic coupling agent 12 and is closely attached to the planar ultrasonic transducer 11 to form an acoustic wave conduction path. In this embodiment, the composite Fresnel acoustic lens 13 and the planar ultrasonic transducer 11 may also be connected directly without using the ultrasonic coupling agent 12.

[0090] In this embodiment, the materials of the first border area 6, the second border area 8, and the rectangular support structure 10 are TC4 titanium alloy, which are prepared by 3D printing technology to facilitate improving the printing accuracy and at the same time enhancing the compressive strength of the cranial window. Among them, the materials of the first border area 6, the second border area 8, and the rectangular support structure 10 are only for illustrative purposes and are not limited thereto. Any materials with biocompatibility and capable of realizing the functions of the first border area 6, the second border area 8, and the rectangular support structure 10 shall fall within the protection scope of the present invention.

[0091] In this embodiment, the materials of the first ultrasonic transmission medium area 7 and the second ultrasonic transmission medium area 9 are polydimethylsiloxane (PDMS), and the mass ratio of its base polymer to the curing agent is 10:1 to facilitate enhancing ultrasonic transmission and reducing energy attenuation by utilizing its good acoustic transmission performance. Among them, the materials of the first ultrasonic transmission medium area 7 and the second ultrasonic transmission medium area 9 are only for illustrative purposes and are not limited thereto. Any other materials with biocompatibility and capable of realizing the functions of the first ultrasonic transmission medium area 7 and the second ultrasonic transmission medium area 9 shall fall within the protection scope of the present invention.

[0092] In this embodiment, the first border area 6, the second border area 8, the first ultrasonic transmission medium area 7, the second ultrasonic transmission medium area 9, and the rectangular support structure 10 in the composite Fresnel acoustic lens can be prepared by various methods such as 3D printing technology, casting technology, and demolding technology.

[0093] The composite Fresnel acoustic lens cranial window structure of the present invention provides a feasible path for a more comprehensive and efficient treatment plan for multiple brain lesion areas, effectively reducing the attenuation and distortion effects of the skull on acoustic signals, reducing the computational cost of generating ultrasonic excitation signals, and having broad application prospects.

[0094] Embodiment 4

[0095] As Figure 7 shown, this embodiment provides a detachable composite Fresnel acoustic lens assembly adapted to a planar ultrasonic transducer, including a stacked composite Fresnel acoustic lens 17, a planar ultrasonic transducer 11, an alternately segmented composite Fresnel acoustic lens 18, a main support fixture base 20, a sub-support fixture module 19, and a transducer-base connection column 21.

[0096] Specifically, secondary support fixture modules 19 are symmetrically arranged on both sides of the superimposed composite Fresnel acoustic lens 17 and the alternately segmented composite Fresnel acoustic lens 18. A rectangular clamping cavity is provided inside the main support fixture base 20, and its inner contour matches the outer dimension of the secondary support fixture module 19. The secondary support fixture module 19 is rigidly locked by axially inserting it into the rectangular clamping cavity. The main support fixture base 20 and the transducer-base connection column 21 adopt an integral connection structure, and the inner diameter tolerance of the transducer-base connection column 21 and the outer diameter tolerance of the planar ultrasonic transducer 11 meet the requirements of interference fit. During assembly, the transducer-base connection column 21 is sleeved on the outer periphery of the planar ultrasonic transducer 11 through the interference fit to complete the rapid installation of the overall assembly.

[0097] Through the modular structure design in this embodiment, the flexibility and functionality of the ultrasonic focusing system are significantly improved. The rapid disassembly and assembly of the lens assembly are realized through the rigid locking of the main support fixture base 20 and the secondary support fixture module 19, effectively ensuring the spatial consistency of the multi-focus sound field. This structure can dynamically switch the lens and simultaneously generate at least three non-coaxial ultrasonic foci in three-dimensional space, providing an efficient and reliable hardware solution for transcranial multi-target therapy.

[0098] In this embodiment, the planar ultrasonic transducer 11 can be used as a standard accessory of the ultrasonic transducer, broadening the application scenarios of a single planar ultrasonic transducer and improving the applicability and effect of transcranial ultrasonic therapy.

[0099] In another implementation manner, the planar ultrasonic transducer 11, especially the composite Fresnel acoustic lens therein, can be customized according to the ultrasonic frequency and the position of the brain region involved in the treatment, providing personalized accessories for users and improving the personalization and effect of transcranial ultrasonic therapy.

[0100] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Compound Fresnel acoustic lens, characterized in that, Comprising: At least two groups of coaxial multi-focus Fresnel zone plates. After translating at least two groups of coaxial multi-focus Fresnel zone plates along the radial direction by a set distance and then superposing them, at least three non-coaxial ultrasonic foci are generated in three-dimensional space, which can be used for transcranial ultrasonic stimulation or treatment of the brain; Wherein, the coaxial multi-focus Fresnel zone plate includes a multi-layer lens structure nested together, and the multi-layer lens structure includes a border area and an ultrasonic transmission medium area.

2. The compound Fresnel acoustic lens according to claim 1, wherein By superposing at least two groups of coaxial multi-focus Fresnel zone plates in a superposition manner, a superposed composite Fresnel acoustic lens is generated, and the overlapping area is retained during superposition.

3. The compound Fresnel acoustic lens according to claim 2, characterized in that, The superposed composite Fresnel acoustic lens includes a first border area and a first ultrasonic transmission medium area, and the first border area is formed by superposing at least two groups of identical coaxial multi-focus Fresnel zone plates along the radial direction.

4. The compound Fresnel acoustic lens according to claim 1, characterized in that, By superposing at least two groups of coaxial multi-focus Fresnel zone plates and then removing the overlapping area, and setting rectangular support structures at certain positions, an alternately segmented composite Fresnel acoustic lens is generated.

5. The compound Fresnel acoustic lens according to claim 4, characterized in that, The alternately segmented composite Fresnel acoustic lens includes a second border area, a second ultrasonic transmission medium area and a rectangular support structure.

6. A design method of a composite Fresnel acoustic lens according to any one of claims 1-5, comprising: Selecting coaxial foci among preset foci to obtain multiple coaxial multi-focus groups, so as to construct coaxial multi-focus Fresnel zone plates; The process of constructing the coaxial multi-focus Fresnel zone plate includes: For each coaxial multi-focus group, arranging the foci in ascending order of focal length: each focus corresponds to a layer of lens structure, the lens structure with a smaller focal length is located in the inner layer, and the lens structure with a larger focal length is located in the outer layer; Based on the ultrasonic wavelength and the preset focal lengths of the respective foci, using the Fresnel half-wave zone theory, calculating the radii of the respective Fresnel zones corresponding to each focus, and the radii of the Fresnel zones include: the radii corresponding to odd wave zone numbers and the radii corresponding to even wave zone numbers; setting the radii corresponding to odd wave zone numbers as the inner diameters of the border areas of the corresponding lens structures, and setting the radii corresponding to even wave zone numbers as the outer diameters of the border areas of the corresponding lens structures; Nesting the lens structures corresponding to each focus. Under the principle that the outer diameter of the border area corresponding to the maximum number of wave zones of the inner layer lens structure is smaller than the inner diameter of the border area corresponding to the minimum number of wave zones of the outer layer lens structure, selecting the number of Fresnel zones of each layer of lens structure to construct a coaxial multi-focus Fresnel zone plate capable of generating coaxial multi-foci; Translating at least two groups of coaxial multi-focus Fresnel zone plates capable of generating coaxial multi-foci along the radial direction by a set distance and then superposing them to construct a composite Fresnel acoustic lens; the processing method after superposition includes: retaining the overlapping area during superposition to generate a superposed composite Fresnel acoustic lens; removing the overlapping area after superposition, and setting rectangular support structures at certain positions to generate an alternately segmented composite Fresnel acoustic lens.

7. Cranial window replacement system, characterized in that, Using the composite Fresnel acoustic lens according to any one of claims 1-5 to replace a part of the skull, and plane ultrasound forms at least three focal spots in the cranial cavity through the composite Fresnel acoustic lens.

8. The cranial window replacement system according to claim 7, wherein The composite Fresnel acoustic lens is fixed to the edge of the cranial window through a biocompatible adhesive to replace the missing skull bone. One side of the composite Fresnel acoustic lens is close to the brain region, and the other side is connected to a planar ultrasonic transducer. Alternatively, the materials of the first border region, the second border region, the first ultrasonic transmission medium region, the second ultrasonic transmission medium region, and the rectangular support structure in the composite Fresnel acoustic lens should all be biocompatible materials.

9. Plane ultrasonic transducer accessories, characterized in that, Comprising: The composite Fresnel acoustic lens according to any one of claims 1-5, with a secondary support fixture module and a primary support fixture base symmetrically arranged on both sides of the composite Fresnel acoustic lens. The primary support fixture base is internally provided with a rectangular clamping cavity, the inner contour of which matches the outer dimension of the secondary support fixture module. Rigid locking is achieved by axially inserting the secondary support fixture module into the rectangular clamping cavity. The primary support fixture base and the transducer-base connection column adopt an integral connection structure. The transducer-base connection column sleeves the outer periphery of the planar ultrasonic transducer and has an interference fit with the planar ultrasonic transducer. The composite Fresnel acoustic lens is nested on the transducer-base connection column.

10. The planar ultrasonic transducer fitting according to claim 9, wherein, The inner diameter tolerance of the transducer-base connection column and the outer diameter tolerance of the planar ultrasonic transducer meet the requirements of interference fit.

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